The following information originally appeared in Naturally Better for You, the magazine about natural products, their health benefits, and where to buy them.
"....How Do Sunscreens Work? Light energy depends on its wavelength. The smaller the wavelength, the greater the energy, and the greater the energy the more the potential damage. UV light is usually broken down into three subtypes: UVA (320-400 nm wavelength), UVB (290-320 nm wavelength), and UVC (200-290 nm wavelength). UVC light will do the most damage to your skin. Fortunately, this kind of light is completely absorbed by the atmosphere. UVB light is responsible for sunburn. UVA light can damage your eyes over time. UVB and UVA go right through the air and clouds, which is why you can still get sunburned when it is overcast. Sunscreens work by preventing some of the UV light reaching your skin. There are 2 types of methods used. Compounds known as chemical sunscreens absorb the UV light, with different chemicals working at different wavelengths. Other compounds are known as physical sunscreens. These are still chemicals, but they work by reflecting the light away from the skin. Sunscreen manufacturers find new chemicals to use in their products over time. One of the newer advances has been to use physical sunscreens in “nanoparticle” form. In the past, physical sunscreens used to show up white on the skin, but the new tiny particles are invisible.
Sunscreens Protect you from Melanoma, Right? Wrong! In February1998, according to a survey of new research by epidemiologist Marianne Berwick of the Memorial Sloan-Kettering Cancer Center in New York, there is no evidence that sunscreen offers any real protection against malignant melanoma, the most dangerous form of skin cancer. “It's not safe to rely on sunscreen," Berwick told the press. More studies prove this and melanoma rates are rising about 6 percent each year whilst sunscreen sales are continuing to climb. Sunscreen makers have engaged in a cynical sleight of hand by claiming that sunscreen helps prevent skin cancer. There are three main kinds of skin cancer: basal cell, squamous cell, and malignant melanoma. The first two are common and almost always medically minor. The American Cancer Society and the National Cancer Institute don't even count them in America’s cancer statistics. Melanoma is much less common, but often fatal. Basal cell and squamous cell skin cancer are caused primarily by UV-B light, the kind that causes sunburn, and there's credible evidence that sunscreen helps prevent those two types of cancer (as well as offers protection against premature ageing of skin). The Food and Drug Administration's SPF (or sun protection factor) rating program measures UV-B protection. But most sunscreens do not offer protection against UV-A, the harmful, longer-wavelength UV light. UV-A penetrates right through the outer skin—and through sunscreen—down to the melanocytes, the cells that become cancerous in melanoma cases. In one study that proved this point, researchers at the Brookhaven National Laboratory in Upton, New York, induced melanoma in fish by exposing them to both UV-B and UV-A sunlight. They concluded: "Sunscreens effective in the UV-B region...would not protect against melanoma." But when people hear the term skin cancer, they think melanoma. That's because when sunscreen labels claim that the product can protect people from skin cancer, consumers don't differentiate melanoma from basal cell and squamous cell skin cancers.
In 1980, an American's lifetime melanoma risk was 1 in 250. Today, it's 1 in 84. Why the rise? One suggestion is that we all spend longer in the sun now. But if you ask any elderly person you know, beaches around the country were jammed on summer weekends in the 1930s. Why didn't a melanoma epidemic hit until the mid-1970s? Does it suggest that there is a 40-year lag between sun exposure and developing melanoma? In fact the research indicates that the lag time could be as low as two years. Lung cancer, heart disease, and other conditions with long lag times are diagnosed at a steady rate year-round. Summer brings no more diagnoses than winter because over, say, 20 years, seasonal distinctions blur. Melanoma diagnoses, on the other hand, do reflect seasonality. At least five studies of melanoma (in Hawaii, the continental U.S., Sweden, Norway, and England and Wales) all agree that melanoma diagnoses follow a seasonal pattern, showing up at a considerably higher rate in summer than in winter. Seasonality is a hallmark of biological events with short lag times.
Some scientists say that ozone depletion may play a role in the higher melanoma rate. However, melanoma cases began to go up a long time before ozone depletion became an issue.
.....…and their Health Effects
Unfortunately, not only are many of the chemical sunscreens common allergens, but they are also linked to increased cancer risk. New Scientist reported that “gender-bending chemicals that mimic the effect of oestrogen are common in sunscreens”. This was referring to research by Margaret Schlumpf from the Institute of Pharmacology and Toxicology at the University of Zurich, Switzerland. Schlumpf and her colleagues tested 6 common UV screening chemicals used in sunscreens, lipsticks and other cosmetics. All 5 UVB screens -benzophenone-3 (oxybenzone), homosalate, 4-methyl-benzylidene camphor (4-MBC, known as enzacamene), octyl-methoxycinnamate and octyl-dimethyl-PABA - behaved like oestrogen in lab tests, making cancer cells grow more rapidly. Only one chemical - a UVA protector called butyl-methoxydibenzoylmethane (B-MDM, known as avobenzene) - showed no activity.
One of the most common sunscreen chemicals, 4-MBC, had a particularly strong effect. When the team mixed it with olive oil and applied it to rat skin, it doubled the rate of uterine growth well before puberty. “That was scary, because we used concentrations that are in the range allowed in sunscreens," Schlumpf says....."
Extract taken from Naturally Better for You.